Wire filter cage

ABSTRACT

An improved filter support structure for supporting filter media. The support structure includes two sections removably coupled together with an improved coupling assembly. The first section has a cross section presenting a first width spaced apart from a second width, the second width being less than the first width. The coupling assembly includes an element carried by the second section, and presents an engagement width that is greater than the second width and less than or equal to the first width such that the element may be shiftably received within the first section at the first width, and can be removably engaged at the second width.

RELATED APPLICATION

[0001] This application is a continuation of application Ser. No.10/037,319 filed Dec. 31, 2001, which claims the benefit of U.S.Provisional Application No. 60/258,674, filed Dec. 29, 2000 and U.S.Provisional Application No. 60/295,333, filed Jun. 1, 2001.

FIELD OF THE INVENTION

[0002] The present invention relates to an air filtration systemsuitable for use within the ventilation system of a building. Moreparticularly, the invention relates to improved filter cages used forsupporting elongated filtration bags or socks within such a filtrationsystem.

BACKGROUND OF THE INVENTION

[0003] Air filtration systems utilized in large ventilation systemsoften employ banks of elongated filtration bags or socks supported bywire filter cage assemblies. The filtration bags are positioned over thefilter cages and remove particulates from the air circulated through thebag. The wire filter cages support the bags and prevent the bags fromcollapsing as air is drawn through the bags. Filter media excludeparticulates from passing through the bag along with the air, and theparticulates accumulate on the outside of the bags as air is drawnthrough the bag and filter cage combination.

[0004] Wire filter cages supporting filtration bags are commonly used inlarge-scale filter assemblies. A large-scale filter assembly structureincludes a large enclosure. The large enclosure is divided by ahorizontal partition plate that separates an upper clean air compartmentfrom a lower dirty air compartment. The partition plate is formed with alarge number of openings arranged in a pattern. Each such openingsupports a wire filter cage and its associated fabric filter bag. Thus,the air flow passes from the lower dirty air compartment through thesuspended filter bags and wire filter cages through the openings in thepartition plate and into the upper clean air compartment.

[0005] Filter bags are periodically cleaned by shaking or by creating abackflow of air from the inside of the filter bags outward. After anextended period of use it becomes necessary to remove the filter cagesand filter bags from the partition plate in order to replace the filterbags. If a one-piece filter cage is employed it is necessary that theupper clean air compartment have sufficient overhead height for theentire length of the filter cage to be accommodated. Wire filter cagescan be as long as 26 feet. Thus, it is preferred, with lengthy filtercages, that the filter cages be partitioned into two or more sections toallow for a shorter overhead height in the clean air compartment. Thisshorter overhead height can result in large cost savings in material andconstruction of large filter assemblies.

[0006] Fine dust can form an explosive mixture with air. Dust collectorsare thus vented to prevent an accumulation of fine dust. Largercollector volume requires a greater vent area. A reduction in overheadheight and consequently volume in the upper compartment leads to a lowerventing cost and associated operating cost.

[0007] A variety of techniques have been used to connect multiplesections of wire filter cages. Wire filter cage section connectionsshould be secure and easily assembled and disassembled, preferablywithout tools. In addition, it is desirable that the inner connectionsbe made without leaving any exposed wire ends or other sharp. Fabricfilter bags are relatively vulnerable. If they are snagged on exposedwire ends they may be torn thereby causing particulate leaks andrequiring replacement of the bags sooner than would otherwise benecessary.

[0008] It is also desirable that wire filter cage sections be assembledwithout the need for fine motor dexterity. Workers replacing filter bagsand handling wire filter cages wear heavy protective clothing includingheavy gloves to protect them. Thus, it would be beneficial if wirefilter cage sections could be assembled and disassembled without theneed for fine manipulation.

[0009] U.S. Pat. Nos. 5,173,098 and 3,747,307 are example of wire filtercage assemblies having exposed ends that may tear filter bags. Otherprior art approaches also may expose wire ends, which may cause damageto fabric filter bags.

[0010] The approach to connecting wire filter cage sections disclosed inU.S. Pat. No. 5,173,098, issued to Pipkorn, reveals a connectiontechnique utilizing two sheet metal sleeves and two wire clips. Thisapproach provides a secure. interconnection that is relatively easy toassemble and disassemble, however it utilizes two sheet metal sleeveswhich add expense and two wire clips which require relatively finemanipulation to connect. In addition, the presence of the two sheetmetal sleeves reduces the surface area available for filtration byinhibiting air flow.

[0011] It would be desirable to have a multi-section wire filter cagethat can be easily assembled and disassembled without the need fortools, and that minimized potential damage to fabric filter bags fromexposed wire ends. Further it is desirable that the wire filter cagethat could be easily manipulated by gloved hands.

SUMMARY OF THE INVENTION

[0012] The present invention in large measure solves the above indicatedproblems by providing a new structure and technique for connecting wirefilter cage sections. The present invention includes formed wire guidesto create a snap latch joint. The wire guides protrude from the interiorof a first wire filter cage section. The wire guides are inserted intothe open end of a second wire filter cage section to join the sections.When the two sections are assembled together on a common axis, theresistance to bending of the wire guides presses the ends of the wireguides against the annular rings of the second wire filter cage, thusaligning the two cages axially and holding the two cages snuglytogether.

[0013] The present invention reduces the overall costs of assemblingwire filter cage joints by elimination of sheet metal sleeves. Betterwelds may be achieved and there is no need for arc welding of thejoints. The ability to use resistive welding equipment to assemble thejoints eliminates the need for buffing of welding flash thereby reducingcost. The wire guides do not need adjustment of the spread of theseassemblies prior to assembling wire filter cage sections. The use ofwire guides also eliminates the need for any additional latching or anyretaining assembly in the joint.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a cutaway perspective view of a large-scale filterassembly that can utilize a plurality of wire filter cages in accordancewith the present invention;

[0015]FIG. 2 is a partial perspective view illustrating the fastening ofa filter element within a filter assembly;

[0016]FIG. 3 is a partial, side sectional view taken along line AA ofFIG. 2;

[0017]FIG. 4 is a partial perspective view illustrating an alternativefastening of a filter element within a filter assembly;

[0018]FIG. 5 is a perspective view of two sections of a wire filter cagein accordance with the present invention;

[0019]FIG. 6 is a plan view of one embodiment of a wire guide inaccordance with the present invention;

[0020]FIG. 7 is an elevational view of the wire guide depicted in FIG.6;

[0021]FIG. 8 is a plan view of an alternate embodiment of a wire guidein accordance with the present invention;

[0022]FIG. 9 is an elevational view of the wire guide depicted in FIG.8;

[0023]FIG. 10 is a plan view of another embodiment of a wire guide inaccordance with the present invention;

[0024]FIG. 11 is a detail view of the wire guide depicted in FIG. 10 anddepicting grip angle and grip range;

[0025]FIG. 12 is a partial elevational view of a wire filter cageincluding two wire guides;

[0026]FIG. 13 is a sectional view of a wire filter cage including twowire guides;

[0027]FIG. 14 is a plan view of an alternate serpent head embodiment inaccordance with the present invention;

[0028]FIG. 15 is a plan view of an alternate arrowhead embodiment of thepresent invention;

[0029]FIG. 16 is an elevational view of the arrowhead embodimentdepicted in FIG. 15;

[0030]FIG. 17 is a plan view depicting alternate angular embodiments ofthe arrowhead embodiment of the invention;

[0031]FIG. 18 is a plan view of another embodiment of the wire guideadapted for use with circular filter cages;

[0032]FIG. 19 is a partial plan view of two circular filter cagesections joined with the wire guide embodiment of FIG. 18;

[0033]FIG. 20 is a sectional view taken along section line BB of FIG.19;

[0034]FIG. 21 is a sectional view taken along section line CC of FIG.19;

[0035]FIG. 22 is an alternate embodiment of the wire guide depicted inFIG. 10;

[0036]FIG. 23 is a sectional view of a wire filter cage assemblyutilizing an alternate embodiment of a wire guide;

[0037]FIG. 24 is a sectional view of a wire filter cage assemblyutilizing an alternate embodiment of a wire guide;

[0038]FIG. 25 is a sectional view of a wire filter cage assemblyutilizing two alternate embodiments of the wire guide;

[0039]FIG. 26 is a perspective view of a wire filter cage assemblyutilizing the embodiment of the wire guide depicted in FIG. 24;

[0040]FIG. 27 is a perspective view of the wire guide depicted in FIG.24;

[0041]FIG. 28 is a perspective view of a wire filter cage assemblyutilizing the embodiment of the wire guide depicted in FIG. 24; and

[0042]FIG. 29 is a perspective view of a wire filter cage assemblyutilizing the embodiment of the wire guide depicted in FIG. 24.

DETAILED DESCRIPTION OF THE INVENTION

[0043] Referring to FIG. 1, a plurality of filter elements are depictedas installed in an air filtration unit 11. The air filtration unit 11broadly includes plenum enclosure 12, base frame 14, air filtrationassembly 15, filtered exhaust duct 16, and air intake duct 17. Airfiltration unit 11 is utilized, for instance, in power or nuclearplants, coal dumping facilities, grain handling facilities and buildingswhere refining operations may take place. Typical ventilation systemsused in these environments may range in height from fifty to one hundredfeet. An access ladder 18, surrounded by safety cage 20, leads up tocatwalk 22, providing access to plenum enclosure 12 through access door24. Filtered exhaust duct 16 and air intake duct 17 may be attached toand integral with plenum enclosure 12. Air filtration assembly 15 ispositioned within plenum enclosure 12. Plenum enclosure 12 is positionedon base frame 14.

[0044] Base 14 may include frame 30, legs 32, and braces 34. Base 14 mayvary in size and proportion, depending on the size of the plenumenclosure 12 to be supported on base 14. Base 14 can be made of avariety of high strength, durable materials such as structural steel.Those of skill in the art will recognize that a variety of materials maybe employed without departing from the scope of the present invention.

[0045] Plenum enclosure 12 may be a large, generally cylindricalstructure, ranging from twenty-five to fifty feet in height. Plenumcover or roof 36 is positioned over plenum enclosure 12. Dust collectionfunnel 38 tapers downwardly toward dust discharge mouth 40. The funnel38 is positioned underneath plenum enclosure 12, residing within thespace below base frame 30 and between legs 32 and braces 34.

[0046] The air filtration assembly 15 is contained mainly within plenumchamber 42. Air filtration assembly 15 comprises an air pressure pump44, pressurization nozzle input duct 46, nozzle arm 48, and numerousfilter elements 50 having air permeable hanging filter media bags orsocks 52 surrounding filter cages 54. In a typical large capacity airhandling system, often employing multiple air filtration units 11, asmany as twenty thousand filter bags 52 and twenty thousand wire filtercages 54 may be utilized. Air pressure pump 44 is connected to suctionnozzle duct 46. Nozzle arm 48 is positioned beneath nozzle duct 46, andhas suction nozzles 56 opening in a downwardly direction, directedtoward bag mouths 58 of filter elements 50.

[0047] Filter media bags or socks 52 are attached to bag mouths 58. Bagmouths 58 are positioned below bag suction nozzles 56. Bag mouths 58rest on and are supported by bag hanger deck 62. Filter media bags 52are positioned over and supported by wire filter cages 54. Unfilteredair enters air filtration unit 11 through intake duct 17 so as to beprocessed through air filtration assembly 15. Filtered air is expelledfrom air filtration unit 11 through filtered exhaust duct 16.

[0048] Referring now to FIGS. 2 and 3, filter element 55 is shown readyfor fastening to hangar deck 62. Bag mouth 58 and filter bag 52 may beheld in position against bag hanger deck 62 by O-rings 78, 78 a whichare positioned inside over-deck bead 80 and under-deck bead 82 of bag52. O-rings 78, 78 a snap into place so as to restrain filter bag 58 andprovide a tight seal, so that no particulate or filtered matter entersplenum chamber 42. Bag mouth 60 is securely fastened to bag hanger deck62 through mounting hole 79 using washer 81 and bolt 83.

[0049] Referring now to FIG. 4, another embodiment of bag mouth 58′ isillustrated. In FIG. 4, bag mouth 58′ is positioned on filter cage 54such that longitudinal wires 84 terminate below the surface of mouth rim77. Bag mouth 58′ is positioned on bag hanger deck 62, and is simplypressed into place and engages with bag hanger deck 62 by friction. Nobolt is utilized to hold bag mouth 58′ to bag hanger deck 62.

[0050] Thus a ventilation system 11 includes a plurality of filterelements 50. Each filter element includes a filter cage 54 and a filterbag 52. As will be appreciated, the filtration unit 11 depicted in FIG.1 can accommodate conventional filter units, filter units in accordancewith the present invention, or a combination of conventional filterunits and units in accordance with the present invention.

[0051] Referring to FIG. 5, an improved wire filter cage 120 inaccordance with the present invention includes a first section 122 and asecond section 124. First section 122 presents a male end 126 and secondsection 124 presents a female end 128. Each section 122, 124 includes aplurality of circular or oval form wires 130 connected by a plurality ofgenerally parallel longitudinal wires 132. First section 122 may furtherinclude a large junction form wire 134 at the end thereof. First section122 includes two guides 136 presenting male end 126 adapted to bereceived into female end 128 of second section 124. Wire guides 136 canbe made out of wire or another suitable material having sufficientelastic memory to return to a relaxed state after deformation.

[0052] Each wire guide 136 includes a pair of generally parallel legs137, and a circular end 139. As can be seen in FIG. 5, the wire guides136 are positioned at opposed ends of the generally race track incross-section wire filter cage section 122.

[0053] Wire guides 136, form wires 130 and longitudinal wires 132 arepreferably joined by resistance welding though other joining methods maybe employed. Whatever joining method is employed, it is desirable thatthe finished product be smoothly finished to prevent snagging or damageto filter bags 52.

[0054] Generally, a wire filter cage 120 will be formed of metal wires.However, it is specifically contemplated that the invention disclosedhere may be used with any type of filter cage or filter support.Examples include but are not limited to filter cages made from plastics,composites and perforated sheet materials.

[0055] Referring to FIG. 5, in operation, wire filter cages 120 areassembled from a first section 122 and a second section 124 by aligningthe first section 122 and the second section 124 coaxially and pressingthe two sections together. In the assembly process, as depicted in FIGS.5 and 13, wire guides 136 engage form wires 130 to secure the joint. Inthis embodiment of the invention wire guides 136 engage form wires 130primarily by friction and outward biasing force.

[0056] A worker disassembling a wire filter cage 120 generally worksfrom above the wire filter cages 120. The worker lifts a wire filtercage 120 to expose the entire length of first section 122 and securessecond section 124 to prevent it from falling. The worker then graspsfirst section 122 and pulls parallel to the longitudinal axis thereof,in order to overcome the retaining force created by wire guides 136.Once the retaining force is overcome, first section 122 and secondsection 124 separate. Second section 124 is then lifted from itsposition below the worker. If a wire filter cage 120 employs more thantwo sections, the disassembly process is repeated for each succeedingpair of sections.

[0057] Referring to FIGS. 6 and 7, an alternative embodiment of wireguide 138 is depicted. Hairpin wire guide 138 is preferably formed of asingle piece of stiff resilient wire and has two generally parallel legs140 and a semicircular end 142. Semicircular end 142 is of the samediameter as the separation of legs 140. Referring to FIG. 7, hairpinwire guide 138 may further include offset 144. Forming will generally beaccomplished by bending but may also be accomplished by othertechniques.

[0058] Hairpin wire guide 138 provides ease of assembly and disassemblybut is limited to applications requiring primarily alignment and a lowretention force. It displays relatively low weak side axial stability.

[0059]FIGS. 8 and 9 depict another embodiment of wire guide 146. Rabbitear wire guide 146 generally includes parallel leg segment 148,diverging leg segment 150 and rounded end 152. Referring to FIG. 9,rabbit ear wire guide 146 may further include offset 154.

[0060] In operation, rabbit ear wire guide 146 is engaged and disengagedin a similar manner to hairpin wire guide 138. Rabbit ear wire guide 146provides a somewhat greater frictional retentive force than hairpin wireguide 138 due to the diverging nature of diverging leg segments 150.

[0061] Referring to FIG. 10, the embodiment of wire guide 136 isdepicted in greater detail. Keyhole wire guide 136 includes generallyparallel legs 137 and circular end 139. The arc of circular end 139extends to greater than about one hundred eighty degrees and less thanabout 300 degrees. Circular end 139 forms a retaining head.

[0062]FIG. 11 shows further detail of wire guide 136. Wire guide 136presents a grip angle 162 and a grip range 164. Grip range 164 extendsfrom closed joint ideal location 166 to acceptable joint location 168.Wire guide 136 may also be modified into another embodiment 136′ asdepicted in FIG. 22 by removing a portion of the wire at the end ofcircular end 160.

[0063] Again referring to FIG. 5, female end 128 of second section 124comprises a generally race track shaped wire 130 having opposed parallelsides 159, and opposed generally circular ends 160. The diameter of theretaining head 139 is sized such that it can be received between the twoparallel sides 137 of wire 130 of female end 128 of section 124, but canbe snapably retained within its respective form wires 130 of female end128. As can also be seen FIG. 5, the wire guides 136 are positioned infirst section 122 such that the retaining heads 139 are received withinthe form wires 130 of female end 128 of second section 124, when the twosections are joined together. Because the retaining heads 139 are of alarger diameter than the distance between the sides of form wire 130 offemale end 128 of the second section 124 at their initial contact point,the retaining heads 139 are urged inwardly as the two sections arepushed together, where the distance between the wires 159 is greater,and then received through the female end 128. Once received through thefemale end 128, the retaining heads 139 snap outwardly behind form wire130, thus engageably retaining the first section 122 with the secondsection 124.

[0064] Note that a cross sectional view of any wire filter cage 120 hasat least a first width and a second width. Even a circular cross sectionhas a greatest chord which is the diameter and a plurality of lesserchords all of which are less in linear dimension than the greatestchord. The guides of the present invention all have significant memory,such that, when urged out of their rest position they are biased toreturn to the rest position. When the wire guides 136, for instance, offirst section 122 are inserted into second section 124, form wires 130of second section 124 urge the wire guides 136 towards each other. Oncethe semicircular head 139 is received past the form wire proximate thefemale end 128 of section 124, the guides 136 are urged back to theirrest position and snapably couple the first and second sectionstogether. The other embodiments act in a similar manner.

[0065]FIG. 14 depicts another embodiment of wire guide 136 as employedin the present invention. Serpent head wire guide 170 includes serpentshaped head 172 and generally parallel legs 173. Serpent shaped head 172presents a widening taper 174 followed by a narrowing taper 175.

[0066] In operation, serpent head wire guide 170 is operated in a mannersimilar to the foregoing embodiments. The serpent head wire guide 170displays ease of insertion because of widening taper 174 and a retentionforce similar to keyhole wire guide 156 because of narrowing taper 175.The serpent head wire guide 170, however, requires more complex toolingto manufacture.

[0067] As depicted in FIG. 15 arrowhead wire guide 176 generallyincludes arrowhead shaped head 178 and generally parallel legs 179.Arrowhead wire guide 176 presents shallow widening taper 180 and steepnarrowing taper 181 Arrowhead wire guide 176 may also include offset 182as depicted in FIG. 12. Referring to FIG. 17, Arrowhead wire guide 176may be constructed with a variety of arrowhead angles 184. A variety ofangles 184 similarly may also be applied to serpent head wire guide 170.

[0068] In operation, arrowhead wire guide 176 is operated in a mannersimilar to the foregoing embodiments. The arrowhead wire guide 176displays ease of insertion and a retention greater than keyhole wireguide 156 because of shallow widening taper 180 and steep narrowingtaper 181. The arrowhead wire guide, however, requires more complextooling to manufacture.

[0069] Referring to FIGS. 18 through 21, another embodiment of the wireguide 186 is depicted. This embodiment of the wire guide 186 isparticularly well adapted for use with wire filter cages 192 of circularcross section. Those skilled in the art will recognize that the cage maytake many different arcuate or polygonal cross-sections withoutdeparting from the scope of the present invention. FIGS. 19, 20 and 21depict wire guide 186 as utilized with wire filter cages 192 of circularcross section.

[0070] Referring to FIG. 23, an alternative embodiment of wire guide186′ is depicted. Guide wire 186′ is similar to guide 186, but includesadditional curvatures. In this embodiment the head or end of the wireguide 186′ includes curve 200 such that the wire guide 186′ contactsform wire 130 in an approximately radial orientation. Wire guide 186′further includes engagement portion 194, arcuate portion 196 and curve200.

[0071] Curve 200 may be applied to any of the previously describedhairpin wire guide 138, rabbit ear wire guide 146, keyhole wire guide156, serpent head wire guide 170, arrowhead wire guide 176 or circularcage wire guide 186. FIG. 24 depicts curve 200 as applied to circularcage wire guide 186′. Referring to FIG. 25 curve 200 may be replacedwith bend 202 or double bend 204. Other configurations will be readilyappreciated by those skilled in the art and the illustrated embodimentsshould not be considered to be limiting. FIGS. 26, 27, 28 and 29 furtherdepict curve 200 as applied to circular cage wire guide 186′.

[0072] It is noted that resistance to bending of the wire guides is amajor factor in joint retention force. Grip angle is a smaller factor.Regardless of the shape of the wire guide employed, when assembled thewire guide grips a form wire 130 of female end 128 of second section124. The retention force of wire guides is a function of the springconstant of the wire, the preset width separating the two wire guides ina joint and the outside dimension of the retention head of the wireguide. The spring constant depends upon the diameter and metallurgicalqualities of the wire employed.

[0073] Referring to FIG. 12, grip range 164 extends from closed jointideal location 166 to acceptable joint location 168. Grip angle 162provides a force tending to hold the connection between first section122 and second section together even if the wire guide is not engagedwith form wire 130 to the closed joint ideal location 166.

[0074] Referring to FIGS. 23 and 24, it is notable that in embodimentsof the wire guide including curve 200, the retention force of the wireguide is enhanced because the force vector created by the spring actionis directed more nearly normal to form wires 130 than wire guideswithout curve 200. As depicted in FIG. 25, it is noted that wire guidecan be formed in other ways to acquire the desired angle of contactbetween wire guide and form wires 130. These are specificallycontemplated to be embodiments of the present invention.

[0075] The multi-sectional nature of the filter cage 120 hereof, and inparticular the ease and reliability with which the sections can besnapped together and pulled apart, facilitate the conservation of spacewithin filter housings. Because the length of the sections is less thanthe length of the whole, the upper, clean portion of filter housings canbe reduced in height.

[0076] The present invention may be embodied in other specific formswithout departing from the spirit of the essential attributes thereof;therefore, the illustrated embodiments should be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than to the foregoing description to indicatethe scope of the invention.

What is claimed is:
 1. A filter element comprising: a support structureincluding a first section and a second section; the first sectionincluding; a first plurality of elongate longitudinal wire members, theelongate longitudinal wire members being generally evenly spaced aboutthe circumference of a circle and generally parallel to one another,each elongate longitudinal wire member having a first end and a secondend, a plurality of form wires, the form wires having a closed circularshape and being of a similar diameter and being positioned inside andperpendicular to the elongate longitudinal wire members, a terminal formwire secured to the first ends of the plurality of elongate longitudinalwire members, a mouth rim secured the second ends of the plurality ofelongate longitudinal wire members, the mouth rim extending beyond adiameter of the form wires in order to secure the first section in anopening in a hanger deck within an air filtration unit; the secondsection including; a second plurality of elongate longitudinal wiremembers, the elongate longitudinal wire members being generally evenlyspaced about a second plurality of form wires of similar diameter to thefirst plurality of form wires and to one another, the form wires havinga closed circular shape and being positioned inside and perpendicular tothe elongate longitudinal wire members, a pair of guide membersextending generally parallel to the second plurality of elongatelongitudinal wire members, the guide members having an elongate U-shapeand two generally parallel legs, the legs of each guide member beingbonded to two of the form wires and extending outwardly and beyond thethird end of the elongate longitudinal wire members and the guidemembers being adapted to slidably fit within the terminal form wire andto resiliently grip the at least two of the first plurality of formwires and to exert an outward force thereon to connect the first sectionand the second section; at least one O-ring having a diameter slightlysmaller than the diameter of the form wires; and a filter medium bagcarried by the support structure, the filter medium bag being sized toencompass both the first section and the second when they are joinedtogether end to end and secured to the first section by tension of theO-ring.